/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.server.ai.mission;

import java.util.logging.Logger;

import javax.xml.stream.XMLStreamException;

import net.sf.freecol.common.io.FreeColXMLReader;
import net.sf.freecol.common.io.FreeColXMLWriter;
import net.sf.freecol.common.model.Colony;
import net.sf.freecol.common.model.Goods;
import net.sf.freecol.common.model.IndianSettlement;
import net.sf.freecol.common.model.Location;
import net.sf.freecol.common.model.Player;
import net.sf.freecol.common.model.Settlement;
import net.sf.freecol.common.model.Tension;
import net.sf.freecol.common.model.Unit;
import net.sf.freecol.common.model.pathfinding.CostDeciders;
import net.sf.freecol.common.util.LogBuilder;
import net.sf.freecol.server.ai.AIMain;
import net.sf.freecol.server.ai.AIMessage;
import net.sf.freecol.server.ai.AIUnit;


/**
 * Mission for bringing a gift to a specified player.
 *
 * The mission has three different tasks to perform:
 * <ol>
 * <li>Get the gift (goods) from the {@link IndianSettlement} that owns the
 * unit.
 * <li>Transport this gift to the given {@link Colony}.
 * <li>Complete the mission by delivering the gift.
 * </ol>
 */
public class IndianBringGiftMission extends Mission
{

    private static final Logger logger = Logger.getLogger( IndianBringGiftMission.class.getName( ) );

    /** The tag for this mission. */
    private static final String tag = "AI native gifter";

    /** The Colony to receive the gift. */
    private Colony colony;

    /** Has the gift been collected? */
    private boolean collected;


    /**
     * Creates a mission for the given <code>AIUnit</code>.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param target The <code>Colony</code> receiving the gift.
     */
    public IndianBringGiftMission( AIMain aiMain, AIUnit aiUnit, Colony target )
    {
        super( aiMain, aiUnit, target );

        this.collected = hasGift( );
    }

    /**
     * Creates a new <code>IndianBringGiftMission</code> and reads the given
     * element.
     *
     * @param aiMain The main AI-object.
     * @param aiUnit The <code>AIUnit</code> this mission is created for.
     * @param xr The input stream containing the XML.
     * @throws XMLStreamException if a problem was encountered during parsing.
     * @see net.sf.freecol.server.ai.AIObject#readFromXML
     */
    public IndianBringGiftMission( AIMain aiMain, AIUnit aiUnit,
                                   FreeColXMLReader xr ) throws XMLStreamException
    {
        super( aiMain, aiUnit );

        readFromXML( xr );
    }


    public Colony getColony( ) { return this.colony; }

    /**
     * Checks if the unit is carrying a gift (goods).
     *
     * @return True if the unit is carrying goods.
     */
    private boolean hasGift( )
    {
        return getUnit( ).hasGoodsCargo( );
    }

    /**
     * Why would this mission be invalid with the given unit?
     *
     * @param aiUnit The <code>AIUnit</code> to test.
     * @return A reason why the mission would be invalid with the unit,
     *     or null if none found.
     */
    private static String invalidMissionReason( AIUnit aiUnit )
    {
        String reason = invalidAIUnitReason( aiUnit );
        IndianSettlement home;
        return ( reason != null )
                ? reason
                : ( ( home = aiUnit.getUnit( ).getHomeIndianSettlement( ) ) == null
                || home.isDisposed( ) )
                ? "home-destroyed"
                : null;
    }

    /**
     * Why would an IndianBringGiftMission be invalid with the given
     * unit and colony.
     *
     * @param aiUnit The <code>AIUnit</code> to test.
     * @param colony The <code>Colony</code> to test.
     * @return A reason why the mission would be invalid with the unit
     *     and colony or null if none found.
     */
    private static String invalidColonyReason( AIUnit aiUnit, Colony colony )
    {
        String reason = invalidTargetReason( colony );
        if ( reason != null ) return reason;
        final Unit unit = aiUnit.getUnit( );
        final Player owner = unit.getOwner( );
        Player targetPlayer = colony.getOwner( );
        switch ( owner.getStance( targetPlayer ) )
        {
            case UNCONTACTED:
            case WAR:
            case CEASE_FIRE:
                return "bad-stance";
            case PEACE:
            case ALLIANCE:
                Tension tension = unit.getHomeIndianSettlement( )
                        .getAlarm( targetPlayer );
                if ( tension != null && tension.getLevel( )
                        .compareTo( Tension.Level.HAPPY ) > 0 ) { return "unhappy"; }
        }
        return null;
    }

    /**
     * Why would this mission be invalid with the given AI unit?
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @return A reason for mission invalidity, or null if none found.
     */
    public static String invalidReason( AIUnit aiUnit )
    {
        return invalidMissionReason( aiUnit );
    }

    /**
     * Why would this mission be invalid with the given AI unit and location?
     *
     * @param aiUnit The <code>AIUnit</code> to check.
     * @param loc The <code>Location</code> to check.
     * @return A reason for invalidity, or null if none found.
     */
    public static String invalidReason( AIUnit aiUnit, Location loc )
    {
        String reason = invalidMissionReason( aiUnit );
        return ( reason != null ) ? reason
                : ( loc instanceof Colony )
                ? invalidColonyReason( aiUnit, ( Colony ) loc )
                : ( loc instanceof IndianSettlement )
                ? invalidTargetReason( loc, aiUnit.getUnit( ).getOwner( ) )
                : Mission.TARGETINVALID;
    }


    // Mission interface
    //   Inherit dispose, getBaseTransportPriority, isOneTime

    /**
     * {@inheritDoc}
     */
    @Override
    public Location getTransportDestination( )
    {
        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location getTarget( )
    {
        return ( this.collected ) ? this.colony
                : getUnit( ).getHomeIndianSettlement( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setTarget( Location target )
    {
        if ( target instanceof Colony )
        {
            this.colony = ( Colony ) target;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Location findTarget( )
    {
        return getTarget( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String invalidReason( )
    {
        return invalidReason( getAIUnit( ), this.colony );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Mission doMission( LogBuilder lb )
    {
        lb.add( tag );
        String reason = invalidReason( );
        if ( reason != null ) return lbFail( lb, false, reason );

        final AIUnit aiUnit = getAIUnit( );
        final Unit unit = getUnit( );
        final IndianSettlement is = unit.getHomeIndianSettlement( );

        while ( ! this.collected )
        {
            Unit.MoveType mt = travelToTarget( getTarget( ), null, lb );
            switch ( mt )
            {
                case MOVE: // Arrived
                    break;

                case MOVE_HIGH_SEAS:
                case MOVE_NO_MOVES:
                case MOVE_NO_REPAIR:
                case MOVE_ILLEGAL:
                    return lbWait( lb );

                case MOVE_NO_TILE:
                    return this;

                case ATTACK_SETTLEMENT:
                case ATTACK_UNIT: // A blockage!
                    Location blocker = resolveBlockage( aiUnit, getTarget( ) );
                    if ( blocker != null
                            && AIMessage.askAttack( aiUnit, unit.getTile( )
                            .getDirection( blocker.getTile( ) ) ) )
                    {
                        return lbAttack( lb, blocker );
                    }
                    moveRandomly( tag, null );
                    continue;

                default:
                    return lbMove( lb, mt );
            }

            // Load the goods.
            lbAt( lb );
            Goods gift = is.getRandomGift( getAIRandom( ) );
            if ( gift == null ) return lbFail( lb, false, "found no gift" );
            if ( ! AIMessage.askLoadGoods( is, gift.getType( ), gift.getAmount( ),
                                           aiUnit ) || ! hasGift( ) )
            {
                return lbFail( lb, false, "failed to collect gift" );
            }
            this.collected = true;
            lb.add( ", collected gift" );
            return lbRetarget( lb );
        }

        // Move to the target's colony and deliver, avoiding trouble
        // by choice of cost decider.
        for ( ; ; )
        {
            Unit.MoveType mt = travelToTarget( getTarget( ),
                                               CostDeciders.avoidSettlementsAndBlockingUnits( ), lb );
            switch ( mt )
            {
                case MOVE_HIGH_SEAS:
                case MOVE_NO_MOVES:
                case MOVE_NO_REPAIR:
                case MOVE_ILLEGAL:
                    return lbWait( lb );

                case MOVE_NO_TILE:
                    return this;

                case MOVE:
                case ATTACK_SETTLEMENT: // Arrived (do not attack!)
                    break;

                case ATTACK_UNIT:
                    Location blocker = resolveBlockage( aiUnit, getTarget( ) );
                    if ( blocker != null
                            && AIMessage.askAttack( aiUnit, unit.getTile( )
                            .getDirection( blocker.getTile( ) ) ) )
                    {
                        return lbAttack( lb, blocker );
                    }
                    moveRandomly( tag, null );
                    continue;

                default:
                    return lbMove( lb, mt );
            }

            // Deliver the goods.
            lbAt( lb );
            Settlement settlement = ( Settlement ) getTarget( );
            boolean result = false;
            if ( AIMessage.askGetTransaction( aiUnit, settlement ) )
            {
                result = AIMessage.askDeliverGift( aiUnit, settlement,
                                                   unit.getGoodsList( ).get( 0 ) );
                AIMessage.askCloseTransaction( aiUnit, settlement );
            }
            return ( result )
                    ? lbDone( lb, false, "delivered" )
                    : lbFail( lb, false, "delivery" );
        }
    }


    // Serialization

    private static final String COLLECTED_TAG = "collected";
    private static final String COLONY_TAG = "colony";


    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeAttributes( FreeColXMLWriter xw ) throws XMLStreamException
    {
        super.writeAttributes( xw );

        xw.writeAttribute( COLLECTED_TAG, this.collected );

        if ( this.colony != null )
        {
            xw.writeAttribute( COLONY_TAG, this.colony.getId( ) );
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void readAttributes( FreeColXMLReader xr ) throws XMLStreamException
    {
        super.readAttributes( xr );

        this.collected = xr.getAttribute( COLLECTED_TAG, false );

        this.colony = xr.getAttribute( getGame( ), COLONY_TAG,
                                       Colony.class, ( Colony ) null );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getXMLTagName( ) { return getXMLElementTagName( ); }

    /**
     * Gets the tag name of the root element representing this object.
     *
     * @return "indianBringGiftMission".
     */
    public static String getXMLElementTagName( )
    {
        return "indianBringGiftMission";
    }
}
